LED lamp

ABSTRACT

A lamp is provided with a full-wave rectifier for convert AC to DC; a SPD electrically connected to the full-wave rectifier for protecting the lamp from voltage spikes; series connected LEDs electrically connected to the SPD; a microprocessor electrically connected to the SPD; series connected MOSFET start circuits electrically to the microprocessor, the MOSFET start circuits configured to switch electronic signals; and resistors each electrically interconnected the LED and the MOSFET start circuit. In response to a normal DC supplied from the SPD, the microprocessor creates a PWM signal to activate the MOSFET start circuits which in turn initiate operations of the LEDs via the resistors respectively. In response to an abnormal DC having voltage spikes supplied from the SPD, the microprocessor deactivates the MOSFET start circuits which in turn direct the DC through the resistors rather than supply the DC to the LEDs via the resistors respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to lamps and more particularly to a light-emittingdiode (LED) lamp with improved starting characteristic.

2. Description of Related Art

LEDs are renowned for their long life and their ability to resist shock.Also, an LED consumes much less electrical power than fluorescent lamps.Therefore, LED lighting devices are gaining popularity worldwide.Recently, LEDs as a light source have been employed in outdoor lightingdevices.

Starting of a fluorescent lamp can be one of preheating, instant start,rapid start, quick-start, semi-resonant start, and programmed start.

However, an LED light having the characteristic of preheating of afluorescent lamp has not been disclosed as far as the present inventoris aware. Thus, continuing improvements in the exploitation of LED lighthaving above characteristic are constantly being sought.

SUMMARY OF THE INVENTION

It is therefore one object of the invention to provide a lamp comprisinga full-wave rectifier for convert alternating current (AC) to directcurrent (DC); a surge protection device (SPD) electrically connected tothe full-wave rectifier for protecting the lamp from voltage spikes; aplurality of light-emitting diodes (LEDs) connected in series andelectrically connected to the SPD; a microprocessor electricallyconnected to the SPD; a plurality of MOSFET (metal-oxide-semiconductorfield-effect transistor) start circuits connected in series andelectrically to the microprocessor, the MOSFET start circuits beingconfigured to switch electronic signals; and a plurality of resistorseach electrically interconnected the LED and the MOSFET start circuit;wherein in response to a normal DC supplied from the SPD, themicroprocessor creates a PWM (pulse-width modulation) signal to activatethe MOSFET start circuits which in turn initiate operations of the LEDsvia the resistors respectively; and wherein in response to an abnormalDC having voltage spikes supplied from the SPD, the microprocessordeactivates the MOSFET start circuits which in turn direct the DCthrough the resistors rather than supply the DC to the LEDs via theresistors respectively.

The above and other objects, features and advantages of the inventionwill become apparent from the following detailed description taken withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an LED lamp according to the invention;

FIG. 2 is a circuit diagram of the LED lamp;

FIG. 3 is a perspective view of the LED lamp; and

FIG. 4 is an exploded view of the LED lamp shown in FIG. 3 with the LEDsremoved.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 4, an LED lamp 100 in accordance with theinvention is shown. The LED lamp 100 is shaped as a fluorescent lamp.That is, the invention is implemented within a typical fluorescent lamp(e.g., T5, T8, T9, or PL lamp) without modification of the shape and theexternal components (e.g., pins) of the fluorescent lamp. The LED lamp100 comprises the following components as discussed in detail below.

A full-wave rectifier consists of two half-wave rectifiers 2 provided atboth ends respectively and is used to convert alternating current (AC)to direct current (DC). A surge protection device (SPD) 1 iselectrically connected to one half-wave rectifier 2 for protecting theLED lamp 100 from voltage spikes. A plurality of (two are shown) LEDs 6connected in series are electrically interconnected the SPD 1 and theother half-wave rectifier 2. A microprocessor 3 is electricallyconnected to the SPD 1. Two MOSFET (metal-oxide-semiconductorfield-effect transistor) start circuits 4 are connected in series andare electrically to the microprocessor 3. Two high resistance members(i.e., resistors) 5 are provided and each high resistance member 5 iselectrically interconnected the LED 6 and the MOSFET start circuit 4.Further, the electrical circuit between the SPD 1 and one LED 6 isgrounded and the electrical circuit between the other LED 6 and theother half-wave rectifier 2 is also grounded.

Operations of the invention are described in detail below. In responseto a normal DC voltage supplied from the SPD 1, the microprocessor 3, asa preheating of a fluorescent lamp, creates a PWM (pulse-widthmodulation) signal to activate the MOSFET start circuits 4. The MOSFETstart circuits 4 having the function of switching electronic signalsinitiate operations of the LEDs 6 via the high resistance members 5respectively.

To the contrary, in response to an abnormal DC voltage (e.g., voltagespikes) supplied from the SPD 1, the microprocessor 3 deactivates theMOSFET start circuits 4 which in turn direct electric current throughthe high resistance members 5 rather than supply electric current to theLEDs 6 via the high resistance members 5 respectively. As a result, theLEDs 6 are protected.

While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modifications within the spirit and scope of theappended claims.

What is claimed is:
 1. A lamp comprising: a full-wave rectifier forconvert alternating current (AC) to direct current (DC); a surgeprotection device (SPD) electrically connected to the full-waverectifier for protecting the lamp from voltage spikes; a plurality oflight-emitting diodes (LEDs) connected in series and electricallyconnected to the SPD; a microprocessor electrically connected to theSPD; a plurality of metal-oxide-semiconductor field-effect transistor(MOSFET) start circuits connected in series and electrically to themicroprocessor, the MOSFET start circuits being configured to switchelectronic signals; and a plurality of resistors each electricallyinterconnected the LED and the MOSFET start circuit; wherein in responseto a normal DC supplied from the SPD, the microprocessor creates apulse-width modulation (PWM) signal to activate the MOSFET startcircuits which in turn initiate operations of the LEDs via the resistorsrespectively; and wherein in response to an abnormal DC having voltagespikes supplied from the SPD, the microprocessor deactivates the MOSFETstart circuits which in turn direct the DC through the resistors ratherthan supply the DC to the LEDs via the resistors respectively.